In my family's house, we periodically have the debate about music. I say "the debate" because I suspect a similar conversation takes place in many homes, especially those with adolescents, pre-teens, and teens. Frankly, the same conversations took place when I was that age in the 60s, and you can only imagine what my parents had to say about MY music. (Put your calculators away - yes, I am somewhat middle-aged and we'll leave it at that.) The conversation was sometimes about volume, but mostly it was about words.
Keeping in mind that these are the most undefined, angst-filled years your child is likely to have in a lifetime, it is important to understand the impact that words have on their development. These kids are searching for identity: from you, from their friends and from the culture around them. I don't think I need to remind anyone that of those three avenues for learning, parents are far and away the least cool (hip, jive, happenin,' down, tight, fresh, etc. etc.), even though your kids love you. As they struggle to not be you (no matter how much they may admire you) you will be struggling to have an impact on their development anyway, as you must. If your children are still young enough (i.e. listening to you at all) you may want to try to influence what they are reading. Books are one area that you can have an almost total look into their minds. If they are old enough to reject your book choices, try reading theirs.
This is actually harder than it sounds. If you show up at basketball practice reading the same book your son's friends know he is reading, it is the kiss of death for his cool quotient (or whatever they're calling it these days). If it's not a book you've already read, try to read it privately. You may have to pretend to just casually notice what they're reading and pretend you read it ages ago, and sidle into the whole BTW, what did they think of it? track. We all know what a mine-field these conversations can be, so try not to make your kids think you are being all Big Brother on them. Kids deserve a very wide range in choosing their own reading material. Censorship isn't the goal here. That said, you do have a right and an obligation to state clearly any objections you may have and why you have them. There are books extreme enough that you can object to having them in your home. Just keep in mind that kids will generally find a way to read what they want to read, and if you have taught them well and laid a good moral foundation for them, they will interpret what they are reading in the sound and moral way you hope.
In trying to set up a Father's Day book display one year, we bumped into a sobering fact. After you left the Easy Reader books and crossed over into Juvenile Fiction, the dads in stories became somewhat less than exemplary. Dads were more often portrayed as absent, abusive, clueless or dead. Try building a cheerful display out of that. The lesson here is to try not to freak out if your kids are reading heavy topics. But don't ignore them either. A conversational opener like, "Wow, that's a pretty heavy book," might be enough to get them to tell you about it. We all read stuff that bears no direct relation to our lives. The fact is, when your kids read stories (true or fictional) about how children experience hard things and fight through them, it can be inspirational. By having a look into the difficult lives of other people, they have a broader world view and can develop empathy and compassion. Possibly the only time you need to feel a threat is when they are consistently reading about the same heavy topics over and over. This could suggest, at minimum, that they have not resolved their thinking about an issue. It is probably not necessary to jump to the conclusion that they are involved in drugs because they read several books that have drug abuse plots or subplots. But it's possible they know of kids who are having these difficulties. When your children hide their current reading or their preferences, it may be time to be concerned.
It does not pay to be overly naive. There are some authors who would gladly pollute your children's minds if it meant making a buck. Sorry - but this really is so. Just like teaching your children to avoid bad people, you need teach them to discern when ideas are bad for them.
Your kids are just as likely to be reading about kids doing positive things. Often, it's more important how a book ends than what is going on in the middle, believe it or not (and within reason). My experience is that the majority of authors for children mean to clearly come down on the side of good and right; to reinforce positive values. On the up side, your children really do prefer to read upbeat, positive and humorous books. They like heroes, problem solvers, and the guy who takes the high road. They still boo the villains. Trust your children's innate goodness.
I am gratified by the number of parents who seem to know what their child prefers to read. Kids trust me to advise them on what to read next, so I have a pretty good idea too. Read what they're reading. Be interested in the topics they find interesting. Talk and listen. If you can keep your kids talking to you, the battle is half won. And take comfort in the fact that kids who read are kids who reason. Readers tend to make better decisions.